JPS59157560A - Electron scanning type ultrasonic flaw detector - Google Patents

Abstract

PURPOSE:To improve the S/N of a detection signal and flow detection performance by selecting either a longitudinal or a transversal wave larger is sound pressure amplitude and performing flaw detection, and setting accurately a parameter for flow detector control, etc. CONSTITUTION:An input device 1 inputs parameters regarding the acoustic velocity in a body to be detected, the angle of incidence of an ultrasonic wave, etc., to an ultrasonic wave beam control circuit 2. The control circuit 2 receives and processes a signal from an ultrasonic wave switching circuit 12 and the inputs from the input device 1 and sends control signals to a pulse oscillator 3, delay circuit 4, etc. The transmitted ultrasonic wave is reflected by a reflector, received by an array probe 5, and inputted to a signal processing circuit 6. The processing circuit 6 uses the control signal of the ultrasonic beam received from an ultrasonic wave beam control circuit to process the received ultrasonic wave signal and sends the processing result to a display device 7. Consequently, a wave of mode with large sound pressure is utilized all the time, so the S/N of the detection signal is improved to improve the flaw detection performance.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an electronic scanning ultrasonic flaw detection device, and in particular, mode conversion between longitudinal waves and transverse waves occurs when ultrasonic waves enter and exit from a measurement system. The present invention relates to an electronic scanning ultrasonic flaw detection device suitable for flaw detection of steel materials, etc.

[Prior art]

Electronic scanning ultrasonic flaw detection equipment has multiple probes arranged in an array, and an electronic circuit controls the direction and phase of the ultrasonic waves emitted from each probe. The technique is developed and put into practical use in the medical field by focusing on the subject and scanning the object by moving the focus over time. In the case of this medical treatment, 1. Since the human body, which is the subject to be examined, is mostly water, all ultrasound waves from the time they are emitted from the probe to the time they are returned are treated as longitudinal waves. .

However, when this technology and equipment is applied to flaw detection of steel materials, etc., longitudinal waves of ultrasonic waves are emitted from the probe, and when they enter the object, they form longitudinal waves at a refraction angle according to Snell's law. A component that propagates into the subject and a component that is mode-converted into a transverse wave and propagates into the subject are generated, and the refraction angles of the longitudinal wave and transverse wave are different. Of course, this path is reversible, and the ultrasonic waves reflected within the subject also return to the probe as longitudinal waves on the opposite path to the incident path. The ultrasound that is reflected as a longitudinal wave inside the subject and returns as a transverse wave is different from the ultrasound that is reflected as a transverse wave inside the subject at a different location, and the sound pressure is different. The sound pressure ratio changes greatly depending on the angle of incidence on the subject. For this reason, in a device similar to that used in the medical field, which always detects as a signal the change in the reversal rate near the focal point of the longitudinal wave component within the subject depending on the presence or absence of positive light, the longitudinal wave component is greatly reduced. When the signal S
There is a drawback that the /N ratio is significantly reduced.

In order to cope with this problem, there are methods in which flaw detection is performed using a component with higher intensity depending on the angle of incidence of the ultrasonic wave on the object to be inspected, such as steel material. In this case, it is necessary to switch the components to be used according to the change in the angle of incidence.
The parameters of the aforementioned control of each probe are varied, and the parameters of the processing of the received signal are correspondingly varied. However, in this type of conventional device, the refractive index and transmittance of longitudinal waves and transverse waves in the object with respect to the incident angle are given based on fixed characteristics that have been theoretically analyzed. did not match, and sufficient improvement could not be obtained.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electronic scanning ultrasonic flaw detection device that eliminates the drawbacks of the prior art described above and can further improve the S/N ratio.

[Summary of the invention]

The present invention focuses on the mode conversion of ultrasonic waves generated at the interface between the object and the medium in contact with it, and performs flaw detection by selecting longitudinal waves or transverse waves, whichever has a larger sound pressure amplitude. The feature is that the parameters for flaw detector control and signal processing corresponding to the selection and the selected mode can be accurately set from the outside based on actual measured values.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, in which a conventional electronic scanning type ultrasonic flaw detector is equipped with an ultrasonic switching circuit comprising an ultrasonic switching circuit 12 and its input device 11, which is a feature of the present invention. The device 13 is added. In the figure, an input device 1 measures the sound velocity of an object to be examined (hereinafter, this will be explained as a steel material).

Control parameters related to the incident angle of ultrasonic waves, etc. are input to the ultrasonic beam control circuit 2. The ultrasonic beam control circuit 2 is
It receives a signal from an ultrasonic switching circuit 12 having an input circuit 11 and an input from an input device 1, performs calculations according to these signals, and connects a pulse oscillator 3, a delay circuit 4, and a signal processing circuit 6. send respective control signals to. The pulse oscillator 3 oscillates a pulse for ultrasound transmission after the delay time of the delay circuit 4 is set by the ultrasound beam control circuit 2. The pulses delayed by the delay circuit 4 are input to the array probe 5, and ultrasonic waves are transmitted. The transmitted ultrasonic waves are reflected by a reflector, received by an array probe and a probe 5, and passed through a delay circuit 4 to a signal processing circuit 6.
is input. The signal processing circuit 6 performs signal processing on the received ultrasound signal using the ultrasound beam control signal received from the ultrasound beam control circuit 2, and sends the processing result to the display device 7. The display device 7 is a general display device such as a CR, T, or printer, and is used to display the results of the signal processing circuit 6. The above is a description of the entire device, but as a preparation for explaining its operation, next we will explain the mode conversion at the interface between water and steel.

Conventionally, in electronic scanning flaw detection equipment, a liquid couplant 21 such as water is placed between an array probe 5 and a steel material 22, as shown in FIG. , the ultrasonic beam 31 is deflected and focused, and the steel material 22 is
The beam scanning within the center and the scanning of the focal point 23 are performed. This control is performed by adjusting the phase of the ultrasonic waves from each probe in the play using the delay circuit 4, and the ultrasonic waves can be focused directly below the array 5 as shown in the left half of FIG. Scanning is performed by deflecting and converging as shown in the right half. By the way, as shown in FIG. 3, the ultrasonic waves (longitudinal waves, transverse waves do not occur in water) output from each probe 32 are refracted and refracted at the interface between the water 21 and the steel material 22, which have different sound speeds. Mode conversion occurs, and transverse waves S are generated in the steel material 22 along with longitudinal waves. Of these, the longitudinal wave is refracted at a refraction angle θL according to the well-known Snell's law, but the refraction angle θS of the transverse wave S is smaller than that of the longitudinal wave. In other words, they move in different directions within the steel material 22. Water 2 from steel material 22 when there is a reflection
1 also follows a reversible path. In this way, not only the path differs depending on the mode, but also the sound pressure. Fourth
The figure shows the change in sound pressure and the relationship between the angle of incidence and the angle of refraction for each mode, which are theoretically determined.The vertical axis shows the round-trip passage rate TL of longitudinal waves and the round-trip passage rate TI+ of transverse waves. There is.

This round-trip passage rate means that when the sound pressure of the ultrasonic wave entering the object (steel) from the contact medium (water) is 100%, the ultrasonic wave of each mode is totally reflected in the steel material, and the ultrasonic wave passes through the opposite path again. The sound pressure when returning to the water is expressed as a percentage. On the other hand, the refraction angles θL and θ6 of longitudinal waves and transverse waves are plotted on the horizontal axis of FIG. 4, and the corresponding incident angles are simultaneously indicated as αL and αS.

In other words, in Fig. 4, the refraction angles θL, θ
Since B is expressed on the same scale, the scales of the corresponding incident angles αL and αS differ depending on the mode.

As shown in the characteristics of FIG. 4, the magnitudes of the round-trip pass rate T8 and TL change when the refraction angle reaches approximately 34°.

For this reason, as described in the conventional example, in a method using only longitudinal waves similar to applications in the medical field, S/N deterioration of the detection signal occurs depending on the scanning position. Therefore, the characteristics as shown in Figure 4 are fixed, and the refraction angle θ0 in the figure is set as the switching angle so that the round-trip passage rates Ts and Tb each stably become larger values. For transverse waves S, θ0 or less, a method using longitudinal waves has been considered. When switching, since the corresponding incident angle for the same refraction angle differs depending on the mode, the scanning position should be changed smoothly by changing the incident angle so that the refraction angle does not change before and after the mode switch. Controls such as this are also performed by the ultrasonic beam control circuit 2. However, in the conventional device using this method, the characteristics shown in FIG. 4 are fixed. However, the speed of sound in steel varies depending on temperature, tree quality, etc. in both longitudinal and transverse wave modes, and the velocity of longitudinal waves in water also varies depending on water temperature. Since the refraction angle also changes in accordance with these speed changes, accurate control was not possible. For this reason, in the embodiment shown in FIG. 1, an ultrasonic switching device 13 is provided to eliminate this drawback (9), and its operation will be explained below.

FIG. 5 is an operational flowchart of the embodiment shown in FIG.

First, in this device, in step 1oo, from input device 1,
Parameters indicating the dimensions of the array probe, the number n of probes, etc., the scanning range, and the scanning pitch are set in the control circuit 2. Among these, the scanning range β is a parameter that limits the refraction angle θ to change within a range of 1θ1<β, as shown in Fig. 6, and within this range, θ is stepped in steps of the size specified by the scanning pitch. It shall be possible to change the In addition, the velocity of water and steel materials (objects) that change due to temperature, etc., the relationship between the refraction angle θ and the incident angle α obtained from the characteristics at that time corresponding to Figure 4, and the boundary between using longitudinal waves and transverse waves. The angle 00, etc. is set from the input device 11 to the switching circuit 12 in step 101. Subsequently, in step 102, the control circuit 2 sets the initial value of the refraction angle θ to θ−β. However, since this initial setting is a different value for each individual probe, it must be set for each probe. For this purpose, if the value of β (10) set in step 100 is for one predetermined probe on probe play 5, then the others are input using this as a reference. The scanning range β1 for each probe can be calculated from the dimensions of the probe, the length of its array, etc., and of course each refraction angle θI will have a different value.Subsequently, in step 103, the scanning range β1 for each probe is calculated. 1θ+Dθ0 for the refraction angle θl of each probe.
It is determined whether or not the boundary angle θ0 inputted in the switching circuit 12 is used, and when there is a mode switching based on the result and the result, the mode corresponding to the mode after the switching such as the speed of sound required for subsequent processing is determined. Transfer the data to the control circuit 2. Step 10
4, as a result of the determination in step 103, 1θ11>β0
For a probe satisfying , the shear wave S corresponding to the incident angle 01 is
Find the incident angle α of the probe from the characteristics shown in FIG.
Determine 1. If the probe satisfies 1θ11<β0, the incident angle αb corresponding to the longitudinal wave and the corresponding delay time τi are similarly determined. Further step 10
4, in step 106 the necessary parameters are set to mode OFF (
11) When there is an exchange, it is transferred to the signal processing circuit 6. In step 105, the ultrasonic waves from each probe have a phase determined by the determined delay time τ1, and the ultrasonic waves are output toward the focal point determined by the phase determined by the determined delay time τ1. and inputs the received signal to the signal processing circuit 6. In step 106, the received signal and the parameters from the control circuit 2 are subjected to necessary processing, and the results are displayed on the display device 7. When this is completed, in step 107, the control circuit 2 decreases each refraction angle θI by the scanning pitch (taken as a negative value), and in step 108 it is determined whether the resulting β1 satisfies 1θ11<β1. If not, this ends as the scanning has ended, but 1θ attack 1〈β
If it is the amount, return to step 103 and repeat the following steps.

Through the above operations, as shown in FIG. 7, the refraction angle θl changes stepwise from β1 to -βI and scanning is performed, and the result U of determination step 103 is output in response to 1θ11≧00. And at the time of this switching, step 1 described above
Data transfer V(12) at 03 is executed. In this way, under the control of the switching circuit 12, each probe can always use waves in modes with higher sound pressure, as shown in FIG. /N ratio is improved, and according to experiments, this improvement amount is about 6 dB. Furthermore, the fourth
Since data representing the characteristics shown in the figure can be easily set from the input device 11 according to the temperature and the material of the subject, accurate mode switching and processing are possible.

〔Effect of the invention〕

As is clear from the above embodiments, according to the present invention, efficient transmission and reception of ultrasonic waves is possible by simply adding a simple ultrasonic switching device to a conventional electronic scanning type ultrasonic flaw detection device. Therefore, the S/N ratio is greatly improved, precision flaw detection is possible, and flaw detection performance is improved.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram showing one embodiment of the present invention, Fig. 2 is an explanatory diagram of the convergence and deflection state of the ultrasound beam, Fig. 3 is an explanatory diagram of the refraction of the ultrasound beam and mode conversion, ) Figure 4 is a diagram showing the theoretical value of the reciprocal passage rate of ultrasonic waves in water and steel, Figure 5 is an operation 70 chart of the embodiment of Figure 1, Figure 6 is an explanatory diagram of the scanning range, and Figure 7 1 is an operation time chart of the embodiment shown in FIG. 1, and FIG. 8 is an explanatory diagram of the operation state of each probe. 1... Input device, 2... Ultrasonic beam control circuit, 3
...Pulse oscillator, 4...Delay circuit, 5...Array probe, 6...Signal processing circuit, 11...Input circuit, 12...Ultrasonic switching circuit, 13... Ultrasonic switching device, 21... Water, 22... Subject, 23... Focal point, 31... Ultrasonic beam, 32... Probe, L...
・Longitudinal wave, S...transverse wave. Agent Patent attorney Masami Akimoto (14) 22 Haku 3 Figure 1 Funeral tJ-Figure Haku 6 Figure Fan q Figure V Shi 21 Engineering → t

Claims (1)

[Claims] 1. Ultrasonic waves output from the individual probes constituting the 7-ray probe and incident on the subject via a liquid contact medium converge at a focal point within the subject, and control means for controlling the phase of the output ultrasonic waves from each probe so that the ultrasonic waves are moved within the subject over time; and the ultrasonic waves incident on the subject are reflected by a wound within the subject, In an electronic scanning ultrasonic flaw detection device equipped with a signal processing means for processing the received signal received by each probe through a reversible path, one longitudinal wave mode propagating in the coupling medium is used. Boundary angle that indicates which mode of longitudinal waves or transverse waves that propagate through the object with different refraction angles corresponding to the ultrasonic waves is selected as the ultrasonic wave for flaw detection of each probe. , and input means for inputting parameters to the control means and signal processing means corresponding to each of the above modes, and in the phase control means, one scanning position specifies the refraction angle of each probe. At each point in time determined by
A function of comparing the refraction angle with the input boundary angle to determine a mode to be used by each of the probes, and causing the control means to control each probe in accordance with the mode pressure; If the determined mode is different from the previous mode, there is a switching function that transfers the input parameters corresponding to the newly selected mode to the control means and signal processing means. An electronic scanning type ultrasonic flaw detection device characterized by having means.